This invention is directed to an absorbent article having an elastic absorbent core. The absorbent core is reinforced and strong thereof using high density bonding lines which extend transverse to the direction of stretching.
There is a trend in the absorbent garment industry to make absorbent articles, such as diapers, more stretchable. In the past, these absorbent articles have been made primarily from inelastic materials. Limited stretchability was accomplished by incorporating elastic bands in the waist and/or leg regions of the garments. More recently, there have been attempts to make these articles elastic throughout.
Absorbent articles contain multiple layers. Disposable diapers, for instance, typically contain a liquid permeable body-side liner, a substantially liquid impermeable outer cover, an absorbent core layer between the body-side liner and the outer cover and, often, a surge management layer on either side of the body-side liner which properly channels a liquid insult toward the absorbent core. To make an absorbent article completely elastic requires that all of the layers be stretchable or extensible, and that at least one of the layers be elastically recoverable. If even one of the layers cannot be stretched, then the entire article cannot be stretched.
Various technologies are known for making the body-side liner and outer cover elastic or stretchable. However, making the absorbent core elastic or stretchable poses a greater challenge. Absorbent core layers often contain a high weight percentage of one or more absorbent media such as wood pulp fibers, fluff, superabsorbent particles or fibers, or the like, entangled and dispersed in a lower weight percentage of a fibrous matrix material. Stretching of the absorbent core can cause tearing of the relatively sparse fibrous matrix, and/or shake-out of the absorbent and superabsorbent materials. There is a need for desire for a stretchable absorbent composite which is able to withstand stretching and retraction with minimal tearing and shake-out.
The present invention is directed to a conformable, comfortable and highly absorbent elastic nonwoven composite which addresses the foregoing concerns.
The absorbent nonwoven composite includes a mixture of nonwoven elastomeric polymer fibers, absorbent fibers, and superabsorbent particles or fibers. The elastomeric polymer fibers may be substantially continuous or staple in length, and preferably are substantially continuous. In one embodiment, the nonwoven elastic polymer fibers constitute less than 20% by weight of the absorbent nonwoven composite, and at least about 3% by weight of the absorbent nonwoven composite. The absorbent fibers and superabsorbent particles or fibers each constitute about 20-77% by weight of the absorbent nonwoven composite. Composites of this general nature are described in U.S. patent application Ser. No. 09/197,268 filed Nov. 20, 1998 in the name of McDowall et al., which is incorporated by reference.
In another embodiment, having higher integrity but somewhat less absorbency, the nonwoven elastomeric polymer fibers constitute about 20-80% by weight of the absorbent nonwoven composite. The absorbent fibers and superabsorbent particles or fibers each constitute about 10-70% by weight of the absorbent nonwoven composite. Composites of this general nature are disclosed in U.S. Pat. No. 5,645,542, issued to Anjur et al., which is incorporated by reference.
The absorbent nonwoven composites are elastic in at least a machine direction. The xe2x80x9cmachine directionxe2x80x9d is the direction of primary orientation of the elastomeric polymer fibers that form the matrix for containing the absorbent and superabsorbent materials. The machine direction corresponds to the direction of movement of a conveying belt or similar apparatus used during extrusion of the elastomeric polymer fibers and combination of the elastomeric polymer fibers with the absorbent and superabsorbent ingredients. When the elastomeric polymer fibers are substantially continuous, one way to determine the machine direction in an absorbent nonwoven composite is to draw a 5 cmxc3x975 cm square on a sample of the composite. Most of the elastic polymer filaments will pass through two of the four sides of the square, thereby defining the machine direction.
In accordance with the invention, the absorbent composite is reinforced by forming a plurality of bond lines transverse to the machine direction. The bond lines can be formed using one or more of ultrasonic bonding, thermal bonding, pressure bonding, and adhesive bonding techniques. Preferably, the bonding creates densified regions along the bond lines.
The bond lines provide the absorbent composite with increased strength and recovery during stretching, and somewhat less extensibility. The increased strength results from stabilization of the elastic polymer fibers, which are anchored or locked into place at the densified, bonded regions. This anchoring at periodic intervals alleviates tearing of the elastic polymer matrix fibers during stretching. The reduced tearing also results in improved elastic recovery of the absorbent composite. Furthermore, the stabilization of the elastic polymer matrix fibers at periodic intervals restricts lateral separation of the fibers, thereby reducing shake-out of the absorbent and superabsorbent material.
With the foregoing in mind, it is a feature and advantage of the invention to provide a reinforced elastic absorbent composite having improved strength and recovery, for use in absorbent articles.
It is also a feature and advantage of the invention to provide a personal care absorbent article with elastic properties, using the elastic absorbent composite of the invention.
It is also a feature and advantage of the invention to provide a medical absorbent article having elastic properties, using the elastic absorbent composite of the invention.
These and other features and advantages will become further apparent from the following detailed description of the presently preferred embodiments, read with the accompanying drawings.